A cheap and easy way to space.

[csmyth3025]

You've missed my point, Jazzman. NOT two ships, two are too inefficient because they cannot get high enough or fast enough to do much good. Although you are right, if you could get the carrier ship to go that fast, seperation would be scary! Not to mention very dangerous.

One ship, perhaps based in part on the SR-71 with an internal rocket added to get it into orbit. Capable of re-entry and landing, to be reused over and over again...

I think the main concept behind air launch is to separate that which works well in an atmosphere (wings for lift and air-breathing jet engines for thrust) from those things that are needed to attain LEO (rocket motors), maneuver and operate in space (thrusters, cooling/heating systems, solar panels for power,etc) and return to Earth (at least a heat shield and parachutes for the crew return vehicle). The latter two items are incorporated in the Russian Soyuz spacecraft and would be incorporated in the US Orion spacecraft in the form of a crew module and a service module. For both the Soyuz and the Orion spacecraft the service module is designed for single-use: it's jettisoned prior to re-entry and allowed to burn up in the atmosphere. Only the crew module is designed for reuse. Current practice is to ground launch Soyuz spacecraft on top of rather large multistage expendable rockets.

The problem with single-stage to orbit concepts is that you have to accelerate all the mass contained in the part of the vehicle that gets you out of the densest part of the atmosphere to ~16,800 mph for LEO. It's more efficient to accelerate only the parts you need to get to orbit and to operate in space: the final stage rocket, the service module, and the crew module (the Soyuz crew module is comprised of an expendable orbital module and a crew return module linked by an inter-module hatch).

Whether you air launch these last three components (four, for the Soyuz spacecraft) at 120,000 ft going at Mach 4 or at 50,000 ft going at 500 mph (~Mach 0.75) is one of those cost/benefit choices that engineers like to work out. Keep in mind that orbital velocity for LEO is roughly equivalent to Mach 25.4 at high altitudes. The complications of taking a mother ship with an attached payload supersonic may outweigh any benefit that the relatively small increase in launch velocity might provide.

Chris

 

[csmyth3025]

On the general subject of "A Cheap and Easy Way to Space" I think the Russians got it right when they developed the Soyuz series of spacecraft. They determined what was needed to get people and (some) supplies to LEO, and they engineered a spacecraft that just met the design criteria for that purpose and no more. The Soyuz has proved to be reliable - with over 100 manned flights since it's first successful manned flight in 1968. Additionally, this same basic vehicle, in the form of the Progress unmanned supply spacecraft, has been used successfully in over 120 missions.

The Soyuz may not be the final answer to cheap access to space, but it seems to have been a better answer than the Space Shuttle. It's lessons are well worth remembering as we lay down plans - and a lot of money - to build a "better" crew vehicle.

I think the 20 million dollar cost per seat for a Soyuz-like astronaut-to-orbit round trip can be significantly reduced if the vehicles we use are mass produced (with emphasis on off-the-shelf parts and, especially, quality work) and air launched.

Chris

 

[halman]

Halman, the only problems I see with your 2 vehicle system is that your space plane starts out too low and too slow. Your carrier vehicle can only get to 50,000 feet and is probably not going much faster than 500 mph.

For your same 100 billion why not build one ship that is a cross between an SR-71 and a shuttle. With SR-71s engines (1960's tech, nothing new there!) the craft can fly to at least 120,000 feet and be travelling two or even three times as fast before firing the rocket engine. Logically speaking, the higher and faster you can be prior to firing your rocket, the better off you are.
The craft would probably look more like an SR-71 with a re-entry shield than a shuttle, but since you were specifically speaking of carrying people only, not cargo, this should work for what you want, and be relatively easy to build since the tech is old hat. If fact, I'm guessing new tech could even improve the jet engines capabilities, allowing you to go faster and higher on less fuel.

Not sure why NASA hasn't tried something like this, theyve owned 3 SR-71s since the Air Force quit using them.

Someday, I am sure that NASA will build a Single-Stage To-Orbit spacecraft, but I don't want them to focus on it right now. Right now, I want to see the simplest, lowest-tech approach possible, while still using a horizontal take-off system. To me, this means two separate vehicles, each specialized in a certain area, to utilize the characteristics of the atmosphere. The weight of the orbiter is critical, because that determines the size of the engines and the amount of fuel that must be carried. The larger the craft, the bigger the fuel load. We need a size that allows the fuel to be carried internally, but will transport at least 10 people, as well as the life-support needed to keep them alive for a while.

If we try to do it all with one vehicle, that vehicle becomes too large to be able to reach orbit. The example that you give of the SR-71 illustrates this point quite well, actually. Even though it can fly higher and faster than any other aircraft, it's airframe is devoted to more fuel storage than any other aircraft. And the SR-71 had to be re-fueled constantly, especially during speed dashes. So there would be no internal space for the rocket needed to push the craft into orbit. The SR-71 is already longer than the space shuttle, so we are talking a vehicle which would exceed the shuttle in size. If the rocket engines and fuel tank were to be reusable, they would push the empty weight up to around what the shuttle weighs empty. This means lots of propellant, more than could be carried internally. And we are still talking about a vehicle which only carries two people.

You say that my approach leaves the orbiter too low, and too slow. In comparison to what? As long as the orbiter is high enough to be able to accelerate at full throttle, and has enough fuel to reach orbit, what difference does it make? If it takes the orbiter 12 minutes of burn time instead of 7, what of it, as long as the engines are reliable? I believe that a design which features 5 engines might be attractive, because engines could be shut down as the g force increases, so that it never exceeds 3 or 4 g's. Also, the larger number of engines means that each engine does not have to be operated at maximum theoretical thrust, which would reduce wear and tear.

When we think about what we have already accomplished, it is difficult to advocate taking small steps. But the small steps we need to take are in a totally different way to reach space. Away from huge vehicles, with massive engines thundering across the land. Away from huge rooms with consoles manned by intent technicians, away from delays caused by weather. I firmly believe that the system that I am advocating will one day carry the bulk of material going into orbit, but, for right now, I just want to see it fly, in a short span of years, so that we can again be called a space faring nation. Once we have it operational, we can begin experimenting with bigger carrier wings, orbiters, more powerful engines, and other refinements. But we need cheap and easy access to space RIGHT NOW!

 

[halman]

On the general subject of "A Cheap and Easy Way to Space" I think the Russians got it right when they developed the Soyuz series of spacecraft. They determined what was needed to get people and (some) supplies to LEO, and they engineered a spacecraft that just met the design criteria for that purpose and no more. The Soyuz has proved to be reliable - with over 100 manned flights since it's first successful manned flight in 1968. Additionally, this same basic vehicle, in the form of the Progress unmanned supply spacecraft, has been used successfully in over 120 missions.

The Soyuz may not be the final answer to cheap access to space, but it seems to have been a better answer than the Space Shuttle. It's lessons are well worth remembering as we lay down plans - and a lot of money - to build a "better" crew vehicle.

I think the 20 million dollar cost per seat for a Soyuz-like astronaut-to-orbit round trip can be significantly reduced if the vehicles we use are mass produced (with emphasis on off-the-shelf parts and, especially, quality work) and air launched.

Chris

The Soyuz has been, hands down, the cheapest and easiest way into space. Even if the space shuttle fleet had been built large enough to allow the flight rates that NASA proposed during its development, cost to orbit probably could not have been made as low as the Soyuz. But the Soyuz only carries three people, and it cannot return to the launch site. For those reasons, it is not the most advanced spacecraft of its type, the space shuttle is. But the space shuttle also was designed as a heavy-lift launch vehicle, which made its payload costs prohibitively high. What we need is a vehicle with the ability of the shuttle to return to the launch site, as well as the ability to carry at least 10 passengers, plus the ability to lift those passengers to orbit cheaper than even the Soyuz can.

I am convinced that this is possible, and can be achieved in a few short years. No major breakthroughs are needed, just the application of what we already know in ways that we have never tried before. An An-225 can already take off weighing 1,323.000 pounds. And this is an aircraft designed for long distance operations, carrying cargo internally, and using 25 year old engine technology. By using a launch catapult, and the latest turbofan engines, there is no doubt in my mind that we could improve on that take-off weight considerably. I am not an engineer, so I throw numbers around kind of casually, but it seems to me that we could build the orbiter much lighter than the space shuttle, even though it would be a similar size. If the fully fueled orbiter weighed less than 1,000,000 pounds, than a carrier wing weighing 1,500,000 pounds fully fueled could probably lift it to launch altitude, provided that the carrier wing did not have to accelerate the weight of the stack to take off speed, which is the function of the catapult or rocket sled. Also, the use of a launch rail, or track, eliminates the need for the carrier wing to have an undercarriage capable of supporting 2,500,000 pounds.

By using a carrier wing, we make possible much higher flight rates, because the carrier wing will not require extensive maintenance after each flight. If we build 4 or 5 orbiters for each carrier wing, we could be launching every couple of weeks. With 10 or 15 orbiters for each wing, we could be launching a couple of times a week. It is not just the cost to put a pound in orbit, but how often we can do it, and the percentage of pounds made up of people which is important, I think. A Soyuz carries three people, one of whom is the pilot. We have got to develop the capability to put several times that number of people in space with each launch, if we are to move launch technology into the modern era.

 

[halman]

Here is a letter that I have written which I ask that all of you who are interested in my proposal copy, print, and mail to your senators and representative. Or, at least email it. But copy it and send it. Please!




President Obama has submitted a budget to Congress which calls for a major change in the goals of American space exploration. I ask you to support this change, because I believe that it is more important at this time for NASA to focus its energies on developing the next generation of spacecraft than any other goal. There has been no major change in the way that we put people into space since the 1950’s. But the space shuttle has shown that a lifting body can be used to return from space, and to land at the point of takeoff, which is essential to economic space flight.

What is needed now is a better way to launch our spacecraft, so that we can operate in a variety of weather conditions, safely, and cheaply. To do this, we must progress from launching our vehicles straight up to a horizontal take-off, two-stage to orbit system. By carrying the spacecraft to high altitude, and flying it off of the back of the carrier aircraft, we can reach orbit with much less effort. Nearly three-quarters of the propellant the space shuttle launches with is used just to reach 100,000 feet, and 1 mile per second. The remaining 4 miles per second is achieved using the final one-quarter of fuel.

This is because the space shuttle is not climbing straight up when it reaches 100,000 feet, it is flying towards the horizon, increasing its speed around the planet. It cannot do this close to the surface, because the air is too dense, and will rip the spaceship apart. Above 50,000 feet, the air is much thinner, and the spacecraft can accelerate much faster. As it accelerates, it climbs higher, which means it can go faster, which results in the planet curving away beneath it.

In the 1960’s, NASA studied an horizontal launch, two-stage to orbit system, using a fly-back booster. This design was scrapped when NASA had to accommodate Air Force demands for payloads the size of box cars, which would weigh many thousands of pounds. The current shuttle design was a response to those demands. If all we want to do is to put people in orbit, a much smaller spacecraft would suffice. A much smaller spacecraft could be lifted by a carrier wing, and flown by conventional turbofan engines to the launch altitude.

What President Obama wants to cancel was an effort to build a rocket to carry astronauts to space, where they would transfer to a vehicle to land on the Moon. This rocket would duplicate the capabilities of several other existing rockets, and would not require advanced technological development. If we are going to be able to realize the benefits of space exploration, such as zero-gravity materials processing, we will need to be able to put people into space on a routine basis, cheaply and safely. This is what NASA needs to be working on, and this is what I urge you to support.

 

[EarthlingX]

Related news from the University of Queensland:

One $14m step towards scramjets for access to space

Published: 27 February 2010
The University of Queensland will lead a $14 million international consortium to help develop scramjet-based access-to-space systems, flying an autonomous scramjet vehicle at eight times the speed of sound – Mach 8, or 8600 km/h.

In parallel, scramjet concepts will be tested at even greater speeds, up to Mach 14, in UQ's world class hypersonic ground-test facilities.

...

Partners in the new program include four Australian universities — UQ, the University of Adelaide, the University of New South Wales, and the University of Southern Queensland; and a US university, the University of Minnesota.

It also includes three international aerospace organisations — DLR in Germany, JAXA of Japan and CIRA of Italy; Australia's Defence Science and Technology Organisation; the Australian Youth Aerospace Association; and industry partners including Brisbane firm Teakle Composites Pty Ltd, Cairns firm AIMTEK Pty Ltd, BAE Systems Australia, and Boeing Research and Technology Australia.

“Access to – getting into – space is necessary for the deployment of space-based systems and technologies for communications, remote sensing, climate monitoring and space science, “ Professor Boyce said.

...

Centre for Hypersonics at UQ

Hyshot

 

[csmyth3025]

Halman,

Your points are well taken. My reference to the Soyuz spacecraft is intended to illustrate the principle that a crew vehicle's design should remain focused on the specific role it's intended to serve. I think we (that's an international "we") have already established the capability to design and build the components needed for a better crew vehicle and launch system. Specifically, a Soyuz-like orbiter and ascent rocket and a heavy-lift airframe that can provide air-launch for such a system. As you've pointed out, one of the advantages of an air launch system is that it permits launching the orbital vehicle above the weather that has traditionally kept ground-based rocket systems sitting on the launch pad.

I can envision a day when the components of manned exploratory vehicles (including supplies and fuel) will be launched by heavy-lift rockets to LEO (perhaps to the ISS) and then assembled in orbit. These orbit-assembled vehicles (more massive than anything that could be launched in a "single throw" from Earth) would then depart to their mission goal (the Moon, Mars, etc.). NASA seems to have finally come to the realization that crew launches should be handled separately. Bigelow is already working on providing a place for the crews to stay as they await the final preparations for their flight from orbit.

These would be our first steps towards establishing a permanent manned presence in space. 100 years from now it might look to our great-great-great grandchildren as crude as Goddard's experimental rockets do to us today. All we can do now is to use the technology we have available and imagine how that technology will develop over time.

Chris

 

[voyager4d]

I agree that making a Soyuz style spacecraft is the place to start, that means making a normal rocket, but make it cheap and reliable. And this is just what SpaceX is trying to do.

Next step is to make a horizontal launch two or three stage launch system. But I’m not sold on the catapult/rocket sled, because then you can’t safely land again without separation first. I also fear that it would be too expensive to maintain this catapult, and last but not least it limits the places where you can launch from.

Third step, something to replace chemical launch systems for LEO transportation.

 

[neutrino78x]

I still think a craft similar to the X-33 is the ultimate horizontal launch vehicle. I heard it was just minor engineering issues that prevented it. Why didn't Lockheed continue that project -- VentureStar -- with their own money? Surely they could have made money from using it as a transoceanic passenger craft (Concorde times 10), if nothing else.

However, as far as launching from a conventional aircraft, could the X-15 not be modified to carry more people? Could it be carried on a C-130 to maximum altitude, then dropped out of the cargo port on the aft end, and fire the rocket to LEO?

Or even carried on the wing of a bomber, like how the X-15 was originally used.

--Brian

 

[Valcan]

I still think a craft similar to the X-33 is the ultimate horizontal launch vehicle. I heard it was just minor engineering issues that prevented it. Why didn't Lockheed continue that project -- VentureStar -- with their own money? Surely they could have made money from using it as a transoceanic passenger craft (Concorde times 10), if nothing else.

However, as far as launching from a conventional aircraft, could the X-15 not be modified to carry more people? Could it be carried on a C-130 to maximum altitude, then dropped out of the cargo port on the aft end, and fire the rocket to LEO?

Or even carried on the wing of a bomber, like how the X-15 was originally used.

--Brian

Far to small. A craft has to be designed for the job it does. The X-15 was designed for carrying one guy very very very fast.

Though something like the X37b might work if scaled up.

http://en.wikipedia.org/wiki/X-37B_OTV-1

And i doubt the C130 could do it. Probably something like the C5 for large loads or just a flying wing. The C130J (best cargo plane EVER) is the newest model and it can olny lift 41,000lbs.

 

[voyager4d]

I still think a craft similar to the X-33 is the ultimate horizontal launch vehicle. I heard it was just minor engineering issues that prevented it. Why didn't Lockheed continue that project -- VentureStar -- with their own money? Surely they could have made money from using it as a transoceanic passenger craft (Concorde times 10), if nothing else.

http://en.wikipedia.org/wiki/Lockheed_Martin_X-33
They thought it would be to expensive to develope without money from NASA..

Lockheed Martin deemed that continuing development of the X-33 privately without government support would not be profitable.

But maby they havn't stoped completly, because in they have had 3 launches in 2007, 2008 and 2009 of a small tech. demonstrator spacecraft under the name "Space Reusable Launch Vehicle".

Recently Lockheed Martin has been testing a new 1/5 scale rocket described to be similar in capabilities and design, known now simply as a "Space Reusable Launch Vehicle". Two tests were conducted secretly at the Spaceport America in New Mexico. The first on December 19, 2007 was billed as a complete success, while the August 12, 2008 launch ended in an irreparable crash after 12.5 seconds of flight.[6][7][8] A third test on October 10, 2009, was another success.[9]

 

[csmyth3025]

Trying to design a single-stage-to-orbit vehicle is somewhat like trying to design a vehicle that will drive you from your house to the airport, roll down the runway, take off, fly you at hypersonic speeds halfway around the world, land, and drive you to your hotel. Expecting one vehicle to do all that is just not reasonable - nor is it necessary.

At the very least, a hypersonic vehicle with rocket boost will have to be air launched at high altitude so that its aerodynamic properties can be optimized for an extremely thin atmosphere and high velocity.

For this reason a "space plane" will have to be launched by ground-based rockets or air launched at high altitude. I think air launching provides better opportunities for re-usability of the launch platform, turn-around time, and cost of maintenance.

Chris

 

[MeteorWayne]

Trying to design a single-stage-to-orbit vehicle is somewhat like trying to design a vehicle that will drive you from your house to the airport, roll down the runway, take off, fly you at hypersonic speeds halfway around the world, land, and drive you to your hotel. Expecting one vehicle to do all that is just not reasonable - nor is it necessary.

Chris

That's one of the best summaries I've ever read.

A+ for saying so much in so few words.

 

[js117]

If, instead, we take off like an airplane, ON an airplane, and wait until we can fly off the back of the that plane and accelerate at full throttle, heading just a little above the horizon, we don't have to have all kinds of redundancy. We can abort and fly back and land. Our engines don't have to produce huge amounts of power to lift us straight up, they just have to be able to accelerate us at about 2 gravities, and we will get there.

Halman, the only problems I see with your 2 vehicle system is that your space plane starts out too low and too slow. Your carrier vehicle can only get to 50,000 feet and is probably not going much faster than 500 mph.

For your same 100 billion why not build one ship that is a cross between an SR-71 and a shuttle. With SR-71s engines (1960's tech, nothing new there!) the craft can fly to at least 120,000 feet and be travelling two or even three times as fast before firing the rocket engine. Logically speaking, the higher and faster you can be prior to firing your rocket, the better off you are.
The craft would probably look more like an SR-71 with a re-entry shield than a shuttle, but since you were specifically speaking of carrying people only, not cargo, this should work for what you want, and be relatively easy to build since the tech is old hat. If fact, I'm guessing new tech could even improve the jet engines capabilities, allowing you to go faster and higher on less fuel.

Not sure why NASA hasn't tried something like this, theyve owned 3 SR-71s since the Air Force quit using them.

They thought of using a supper XB-70 space launch system.

http://www.abovetopsecret.com/forum/thread60762/pg1

http://robocat.users.btopenworld.com/xb70.htm

 

[neutrino78x]

Maybe a better example of what I was thinking of would be a Lynx rocketplane.

--Brian

 

[csmyth3025]

js117,

Again, we encounter the debate about whether "high and fast" is more cost effective than "low and slow". In this debate, however, we need to keep in perspective what these two terms really mean.

The ISS orbits at an altitude between 178 miles and 286 miles. For the sake of argument, let's say that we want our crew vehicle to be able to attain an orbit of 230 miles and a velocity of 17,230 mph (~Mach 26.3 in the Statospere) . This would put it in the range to dock with the ISS, whose average speed is 17,227 mph according to Wikipedia. It should be noted that the ISS is the only LEO destination that our crew vehicle has available at this tine.

Generally, the Stratosphere starts at about 36,000 ft (~6.8 miles) and extends upward from there to about 31 miles. The interesting thing about Mach numbers at high (stratospheric) altitudes is that its value remains about the same (~655 mph) as altitude increases. Our "low and slow" air launch would release the orbiter at about 50,000 ft (~9,5 miles high). This altitude represents about 4.7% of the total altitude needed. Likewise, our 500 mph launch speed (Mach 0.76) represents about 3% of our final velocity.

Our "high and fast" launch vehicle might attain an altitude of about 75,000 ft (~14.2 miles). This represents about 6.2% of the total altitude needed (an increase of 1.5%). Likewise, if our craft achieved a velocity of Mach 3, this would represent about 7.7% of the velocity needed (an increase of about 4.7%).

The question is: How much extra cost and design complications can be justified by these relatively small increases in launch altitude and forward velocity"

Chris

 

[halman]

I agree that making a Soyuz style spacecraft is the place to start, that means making a normal rocket, but make it cheap and reliable. And this is just what SpaceX is trying to do.

Next step is to make a horizontal launch two or three stage launch system. But I’m not sold on the catapult/rocket sled, because then you can’t safely land again without separation first. I also fear that it would be too expensive to maintain this catapult, and last but not least it limits the places where you can launch from.

Third step, something to replace chemical launch systems for LEO transportation.

The Soyuz is a wonderful spacecraft, proven and reliable. However, it is not capable of landing on an airstrip, instead needing a very large target area free from people and obstructions. The Soyuz represents the first level of technology for space exploration, with minimal weight, ballistic re-entry, and no cross-range capability. I am sure that we can do better, and I also believe that an off-planet industrial revolution will require better, simply because of the personnel requirements. Hundreds of people are going to be needed to build and operate the space stations that will serve as the laboratories for the dozens of scientists who will be employed to find new technologies. Someday, the orbital factories will largely be automated, but, by that time, we will be launching deep space probes several times a year, mining the Moon, and expanding the sphere of human activity. Which will require people.

The catapult offers the safety of being able to abort a take-off at the point of take-off, and still stop the stack completely. Once airborne, the orbiter can separate from the carrier wing and come around to land, perhaps dumping fuel part of the way. The same holds true after a normal launch; if a problem arises, an abort to the point of origin is possible. This is why I believe that the lifting body will supplant the capsule, because it can be flown like an airplane.

Also, we can build more than one catapult, once we have proven the technology, and I am sure than we will. But there probably won't be a bunch of them, just as few places have airports that can handle fully loaded 747's.

 

[csmyth3025]

Maybe a better example of what I was thinking of would be a Lynx rocketplane.

--Brian

Perhaps something like a scaled-up Lynx rochet plane is the future. The Russian Buran space plane (tested but never deployed) is an example of how such a scaled-up version might look. On the surface the Buran looks like a carbon-copy of the Space Shuttle, but it has more in common with the Lynx than the Shuttle - particularly in regard to propulsion.

I'm still convinced that a lifting wing (or mother ship, if you prefer) is preferable to ground-based rocket launch. The use of a catapult system is certainly feasible - the US Navy routinely uses catapult systems on their carriers. A land based catapult system might shorten the runway length and maximize the take-off weight of the mother-ship/orbiter combination vehicle. Landing gear for the mother ship would not be replaced by the catapult system, it would be designed to work in conjunction with this type of take-off assist. A JATO system (jet assisted take off - which is really a rocket assisted take off) might also be considered in place of or in addition to a catapult system. I'm thinking that using JATO might create more problems than it solves, though.

On the subject of the disadvantages of using a Soyuz-type orbiter (it needs a large unpopulated landing quadrant) - keep in mind that our "experts" chose this very method for return of the Orion crew module. I'm certainly not saying that it's preferable to landing back at the space port. The advantage right now is that we (an international "we") already have a system with a long and reliable track record that employs this method.

People like to think that we can develop a cheap and easy way to space. They mention space elevators and rail guns, among other things. Until we make breakthroughs in material science and physics, we're stuck with blasting off from our planet with chemical rockets. The issue at present is how to do this most efficiently.

Chris

 

[neutrino78x]

Well a railgun would be another good idea, you could use a magnetic levitation track to accelerate the craft to the speed where a ramjet would work, then engage said ramjet to get into space, then use LOX+H2 in space.

--Brian

 

[halman]

csymth3025,

In my visualization, a launch rail is indispensable, because the stack will weigh in at around 2,500,000 pounds. An undercarriage that could support that amount of weight is going to weigh hundreds of thousands of pounds, which is totally unnecessary. A cradle, which rolls along the launch track, can support the weight of the two vehicles, and act as the driven element in the catapult. This way, the stack is removed somewhat from the powerful magnetic fields of a railgun. The term 'catapult' implies rapid acceleration, which is misleading, I think. What is desired is to be able to accelerate the stack smoothly to a speed where the carrier wing has several tons of positive lift, so that it will fly out of the cradle, which I estimate will be at about 300-350 miles per hour. This insures positive control once the stack is airborne, and avoids the fuel penalty involved in the carrier wing's engines being solely responsible for accelerating the stack from a standing start.

The launch track also offers a safe way to abort a take-off if a failure occurs, allowing the stack to be brought to a stop quickly and without damage. Once the carrier wing has separated from the orbiter, and consumed the majority of its fuel, it will weigh considerably less than at take-off. Therefore, its undercarriage would be much lighter. Even that could be dispensed with if a way were found to land the carrier wing in the cradle, but I am not going to complicate the system by saying that that should be a goal. If an electromagnetic catapult is not readily feasible, then a rocket powered system to propel the cradle would work, if it were able to be shut down.

The whole idea behind this concept is to specialize the components as much as possible, and to utilize every advantage. Using ground based power to get the stack moving faster than stall speed is one advantage, and avoiding a heavy undercarriage is another. This also avoids having to build a runway several miles long that could support the weight of the stack, because the carrier wing engines would take quite a while to build up speed under that kind of load.

As far as I am concerned, any ballistic re-entry vehicle has to come down in the ocean, or in a completely unpopulated area. Everybody talks about how accurate the Soyuz re-entries have been, and their record is impressive, as long as you remember that the bull's eye is miles across. A ballistic re-entry vehicle is the cheapest way to return from space, but is just as susceptible to burning up as a lifting body is, if the angle of re-entry is wrong. Over time, the capsule loses the economic advantage, because the service module is discarded each flight, and recovery costs keep adding up. Properly designed, the system that I am advocating would probably be in use for at least 50 years, and quite possibly longer, perhaps becoming the standard launch system until we achieve the space elevator.

 

[csmyth3025]

Halman,

You may be right about a launch track (rail). I found these two items in the Wikipedia article on rail speed records:

"...The Japanese JR-Maglev is the fastest non-conventional train in the world, having achieved 581 km/h (361 mph) on a magnetic-levitation track..."

and

"...The French TGV (Train à Grande Vitesse) is the fastest conventional train in the world, using powered metal wheels riding on metal rails. In April 2007, the TGV broke its own 1990 record with a new speed of 574.8 km/h (357.18 mph) under test conditions with a shortened train (two power cars and three passenger cars) and larger wheels to reduce angular speed in the motors..."

In both cases these trains were able to achieve speeds that you feel would be sufficient to launch a mother ship/orbiter combination. I'm not sure that a mag-lev could be designed to sustain the weight, but I may be wrong about that.

Assuming that a rail system could be constructed for launches, the mother ship will still need landing gear in order to make a conventional landing at the space port or, if need be, at another airport. If the landing gear only has to handle the stress and load of the mother ship on landing it wont have to be as robust (and heavy). This brings up the question of abort procedures: is there a scenario wherein the launch would have to be aborted after take off and the mother ship would have to land fully loaded with the orbiter? If so, there will be no weight savings on the design of the landing gear. Even so, a rail launch would allow for a higher maximum take off weight.

Chris

 

[js117]

by halman


In my visualization, a launch rail is indispensable, because the stack will weigh in at around 2,500,000 pounds. An undercarriage that could support that amount of weight is going to weigh hundreds of thousands of pounds, which is totally unnecessary. A cradle, which rolls along the launch track, can support the weight of the two vehicles, and act as the driven element in the catapult. This way, the stack is removed somewhat from the powerful magnetic fields of a railgun. The term 'catapult' implies rapid acceleration, which is misleading, I think. What is desired is to be able to accelerate the stack smoothly to a speed where the carrier wing has several tons of positive lift, so that it will fly out of the cradle, which I estimate will be at about 300-350 miles per hour. This insures positive control once the stack is airborne, and avoids the fuel penalty involved in the carrier wing's engines being solely responsible for accelerating the stack from a standing start.


This launch rail system was used in and old classic Science Fiction Movie " When Worlds Collide " made in 1951.
If you have seen the movie is this what you are talking about.

 

[scottb50]

by halman


In my visualization, a launch rail is indispensable, because the stack will weigh in at around 2,500,000 pounds. An undercarriage that could support that amount of weight is going to weigh hundreds of thousands of pounds, which is totally unnecessary. A cradle, which rolls along the launch track, can support the weight of the two vehicles, and act as the driven element in the catapult. This way, the stack is removed somewhat from the powerful magnetic fields of a railgun. The term 'catapult' implies rapid acceleration, which is misleading, I think. What is desired is to be able to accelerate the stack smoothly to a speed where the carrier wing has several tons of positive lift, so that it will fly out of the cradle, which I estimate will be at about 300-350 miles per hour. This insures positive control once the stack is airborne, and avoids the fuel penalty involved in the carrier wing's engines being solely responsible for accelerating the stack from a standing start.

Once you are airborne you are in pretty much the same place you would be on the ground, it's still going to require rockets to get to orbit, that could probably pretty much get you there directly a lot easier, and much cheaper. Escape provisions from the pad, or rail to orbit are another requirement.

 

[csmyth3025]

Once you are airborne you are in pretty much the same place you would be on the ground, it's still going to require rockets to get to orbit, that could probably pretty much get you there directly a lot easier, and much cheaper. Escape provisions from the pad, or rail to orbit are another requirement.

To say that "Once you are airborne you are in pretty much the same place as you would be on the ground..." is correct in terms of the distance from the Earth's center and, thus, the strength of the gravitational field at the air launch altitude. The advantage of air launch from a carrier wing (mother ship) has more to do with the atmosphere than with gravity, though. The density of the atmosphere at ~53,000 feet is about 1/10 that at sea level. This reduced density allows you to go faster with less air resistance (drag) on your booster rocket/orbiter assembly. Also, at this altitude your launch point is above most forms of air turbulence and all of the types of weather systems that might interfere with your launch. Wikipedia concisely sums up these benefits in their article on "air launch to orbit", the relevant portion follows:

"...The main advantage realized by the Pegasus air launch system, currently the only orbital air launch provider, is flexibility. Air launch to orbit offers the potential for aircraft-like operations such as launch on demand, and is also less subject to launch-constraining weather. This allows the aircraft to fly around weather conditions as well as fly to more optimal launch points. Other advantages include reduced national range scheduling constraints, minimum launch site requirements, and reduced range safety concerns, and equatorial launch from the U.S.

One advantage of air launching is the considerable amount of propellant conserved. This is because the carrier aircraft is able lift the rocket to altitude much more efficiently with use of turbojet engines, which do not require onboard storage of an oxidizer. This allows the launch system to conserve a significant amount of mass that would otherwise be reserved for fuel, reducing overall size. A larger fraction of the rocket mass can then include payload, thus reducing payload launch costs. Launching at altitude also presents significant performance benefits to the rocket. The high horizontal speed provided by the aircraft gives the rocket a large initial velocity and reduces the delta V required to reach orbit. Figure 1 below indicates that high speeds can reduce delta V requirements up to 15% over the vertical launch case.

Cost calculations show that a supersonic air launch system has the potential to reduce launch costs over conventional vertical takeoff vehicles by an order of magnitude...."

One additional advantage not mentioned in the excerpt is the relatively low cost with which the mother ship can be "turned around" (with normal aircraft maintenance procedures) for the next orbital launch. It's important to note that air launch is, at this time, considered a good candidate for launching crewed vehicles (and, perhaps, routine resupply) to the ISS or other Low Earth Orbit destinations - should any other such destinations develop in the future. Heavy lift launches of massive payloads would still be handled by ground launched rockets until a more efficient system is found.

Chris

 

[neutrino78x]

So could we make an X-33 type rocketplane that launched horizontally, like an airplane? Like I said, like that Lynx rocketplane, except using hydrogen and oxygen instead of hydrocarbon (for environmentally clean exhaust). Still can't believe they canceled the X-33, it was a great idea.

--Brian